Various types of radar systems and target detection techniques are known. Two radar systems capable of detecting a target object at a relatively short-range include the step-frequency radar and the frequency-modulated, continuous-wave radar.
A step-frequency radar produces a carrier signal having a frequency that is stepped by predetermined interval frequencies. Return signals are processed at each of the intervals or steps from which range information is determined. Two significant limitations associated with the use of a step-frequency radar in short-range applications are its limited unambiguous ranging capability and the significant difficulty of implementing range gating for short-range applications. Range gating, in general terms, is a technique that improves the sensitivity of a short-range radar by suppressing reflections up to the point of the antenna reflection. Such undesirable reflections, if left unabated, would generally render undetectable the relatively low energy return signals received from a short-range target object.
When a step-frequency radar is operated monostatically, for example, the return signal is corrupted by reflections from the antenna feed, which significantly degrades the sensitivity of the system. Although range gating for a step-frequency radar is technically implementable, very fast switches must be employed on the transmit and receive channels to gate out undesired antenna reflections. Because switching times must be on the order of nanoseconds in typical short-range applications, a range gating implementation for a step-frequency radar which utilizes such switches is complex, costly, and is often unable to reliably provide for relatively large unambiguous step frequency ranges. It is noted that the range of the step-frequency radar is limited by the number of its frequency steps.
Several of the problems associated with the step-frequency radar may be overcome by using a frequency-modulated, continuous-wave radar system, although this approach has associated with it a number of deficiencies and limitations that negatively impact the efficacy of such radars in short-range applications. Although a frequency-modulated, continuous-wave radar approach offers the opportunity to implement range gating in a generally straightforward manner and typically provides for an unambiguous ranging capability superior to that of a step-frequency radar, the resolution of the frequency-modulated, continuous-wave radar is significantly poorer than that of a step-frequency radar.
There exists a need for a radar system and detection method that overcomes these and other limitations associated with step-frequency and frequency-modulated, continuous-wave radars. There exists a further need for such a system and method that provides for accurate target detection and range determination in short-range applications. The present invention fulfills these and other needs.